Guanylyl cyclase C (GCC) (also known as STAR, ST Receptor, GUC2C, and GUCY2C) is a transmembrane cell surface receptor that functions in the maintenance of intestinal fluid, electrolyte homeostasis and cell proliferation (Carrithers et al., Proc Natl Acad Sci USA 100: 3018-3020 (2003); Mann et al., Biochem Biophys Res Commun 239: 463-466 (1997); Pitari et al., Proc Natl Acad Sci USA 100: 2695-2699 (2003)); GenBank Accession No. NM.sub.-004963, each of which is incorporated herein by reference). This function is mediated through binding of guanylin (Wiegand et al. FEBS Lett. 311:150-154 (1992)). GCC also is a receptor for heat-stable enterotoxin which is a peptide produced by E. coli, as well as other infectious organisms (Rao, M. C. Ciba Found. Symp. 112:74-93 (1985); Knoop F. C. and Owens, M. J. Pharmacol. Toxicol. Methods 28:67-72 (1992)). Binding of ST to GCC activates a signal cascade that results in enteric disease, e.g., diarrhea.
GCC is expressed at the mucosal cells lining the small intestine, large intestine and rectum (Carrithers et al., Dis Colon Rectum 39: 171-181 (1996)). GCC expression is maintained upon neoplastic transformation of intestinal epithelial cells, with expression in all primary and metastatic colorectal tumors (Carrithers et al., Dis Colon Rectum 39: 171-181 (1996); Buc et al. Eur J Cancer 41: 1618-1627 (2005); Carrithers et al., Gastroenterology 107: 1653-1661 (1994)). GCC expression has also been detected in esophageal cells diagnosed as Barrett's esophagus, esophageal cancer and gastric cancer.
The tissue-specific expression and association with cancer, e.g., of gastrointestinal origin, (e.g., colon cancer, stomach cancer, or esophageal cancer), can be exploited for the use of GCC as a diagnostic marker for this disease (Carrithers et al., Dis Colon Rectum 39: 171-181 (1996); Buc et al. Eur J Cancer 41: 1618-1627 (2005)).
Cancer is a leading cause of death worldwide, accounting for >7 million deaths each year. Cancer mortality is nearly universally related to the spread of primary tumors to distant sites forming metastases and ultimately leading to death. This is particularly true for colorectal cancer in which an inverse relationship exists between disease spread and prognosis. Guanylyl Cyclase C (GCC) is a member of the particulate family of guanylyl cyclases and is found selectively on the apical surfaces of intestinal epithelial cells. Importantly its expression is maintained on 100% of differentiated primary metastatic tumors arising from the colon and can be targeted for diagnostic and therapeutic purposes. The advent of monoclonal antibody (mAb) technology has made a prodigious impact on biochemical and immunoassays as well as cancer therapeutics and diagnostics.
As a cell surface protein, GCC can also serve as a therapeutic target for receptor binding proteins such as antibodies or ligands. In normal intestinal tissue, GCC is expressed on the apical side of epithelial cell tight junctions that form an impermeable barrier between the luminal environment and vascular compartment (Almenoff et al., Mol Microbiol 8: 865-873); Guarino et al., Dig Dis Sci 32: 1017-1026 (1987)). As such, systemic intravenous administration of a GCC-binding protein therapeutic will have minimal effect on intestinal GCC receptors, while having access to neoplastic cells of the gastrointestinal system, including invasive or metastatic colon cancer cells, extraintestinal or metastatic colon tumors, esophageal tumors or stomach tumors, adenocarcinoma at the gastroesophageal junction. Additionally, GCC internalizes through receptor mediated endocytosis upon ligand binding (Buc et al. Eur J Cancer 41: 1618-1627 (2005); Urbanski et al., Biochem Biophys Acta 1245: 29-36 (1995)).
Polyclonal antibodies raised against the extracellular domain of GCC (Nandi et al. Protein Expr. Purif. 8:151-159 (1996)) were able to inhibit the ST peptide binding to human and rat GCC and inhibit ST-mediated cGMP production by human GCC.
GCC has been characterized as a protein involved in cancers, including colon cancers. See also, Carrithers et al., Dis Colon Rectum 39: 171-181 (1996); Buc et al. Eur J Cancer 41: 1618-1627 (2005); Carrithers et al., Gastroenterology 107: 1653-1661 (1994); Urbanski et al., Biochem Biophys Acta 1245: 29-36 (1995).
A nucleotide sequence for human GCC is disclosed as GenBank Accession No. NM.sub.-004963, which is incorporated herein by reference.
Amino acid sequence for human GCC is disclosed as GenPept Accession No. NP.sub.-004954, which is incorporated herein by reference.
Monoclonal antibodies specific for GCC include GCC:B10 (Nandi et al., J. Cell. Biochem. 66:500-511 (1997)), GCC:4D7 (Vijayachandra et al. Biochemistry 39:16075-16083 (2000)) and GCC:C8 (Bakre et al. Eur. J. Biochem. 267:179-187 (2000)). GCC:B10 has a kappa light chain and an IgG2a isotype and cross-reacts to rat, pig and monkey GCC. GCC:B10 binds to the first 63 amino acids of the intracellular domain of GCC (Nandi et al. Protein Sci. 7:2175-2183 (1998)). GCC:4D7 binds to the kinase homology domain, within residues 491-568 of GCC (Bhandari et al. Biochemistry 40:9196-9206 (2001)). GCC:C8 binds to the protein kinase-like domain in the cytoplasmic portion of GCC.
U.S. Pat. No. 5,518,888, which is incorporated herein by reference, discloses compositions including anti-GCC antibodies which in some embodiments may be conjugated to active agents. Methods using the compositions are disclosed including methods of imaging and methods of treating metastatic colorectal cancer.
U.S. Pat. No. 5,601,990 and patents and applications claiming common priority, which are each incorporated herein by reference, disclose methods using anti-GCC antibodies including methods diagnosing colorectal cancer, methods of determining the origin of adenocarcinomas of unconfirmed origin and methods of detecting the extent of primary colorectal tumor invasion of the intestinal/colon wall.
U.S. Pat. No. 5,518,888 and patents and applications claiming common priority, which are each incorporated herein by reference, disclose compositions including anti-GCC antibodies which in some embodiments may be conjugated to active agents. Methods using the compositions are disclosed including methods of imaging and methods of treating metastatic colorectal cancer.
U.S. Pat. No. 6,767,704 and patents and applications claiming common priority, which are each incorporated herein by reference, disclose methods using anti-GCC antibodies including methods diagnosing, imaging and treating primary and metastatic esophageal and stomach cancer.
PCT application PCT/US10/053,733 and provisional applications 61/107,613 and 61/254,119, which are each incorporated herein by reference, disclose T cells which express fusion proteins that comprise an anti-GCC antibody portion on the cell surface and methods of making and using such T cells.